Coated tool, and cutting tool comprising same

ABSTRACT

A coated tool of the present disclosure is provided with a base member and a coating layer located on a surface of the base member. The coating layer includes a TiCNO layer and an Al 2 O 3  layer. The Al 2 O 3  layer is located in contact with the TiCNO layer at a position farther from the base member than the TiCNO layer is. The TiCNO layer includes a composite protrusion including a first protrusion that projects toward the Al 2 O 3  layer, a second protrusion that projects from the first protrusion in a direction intersecting a direction in which the first protrusion projects, and a third protrusion that projects from the second protrusion in a direction intersecting the direction in which the second protrusion projects.

TECHNICAL FIELD

The present disclosure relates to a coated tool including a coating layer on a surface of a base member and a cutting tool including the coated tool.

BACKGROUND

A coated tool such as a cutting tool has been known in which a coating layer formed by laminating an Al₂O₃ layer is formed on a surface of a base member such as a cemented carbide, a cermet or a ceramic through a bonding film.

With the recent increase in the efficiency of a cutting process, cutting tools are increasingly used in heavy intermittent cutting where large impacts are applied to the cutting edge. Under such severe cutting conditions, a large impact is applied to the coating layer, and chipping or peeling of the coating layer tends to occur. Therefore, improvement of fracture resistance is required for the coating layer in addition to wear resistance.

As a technique for improving the fracture resistance in the cutting tool, Patent Document 1 discloses a technique in which a bonding film and an Al₂O₃ layer are formed sequentially, and a dendrite extending toward the Al₂O₃ layer side and a branched protrusion extending from the dendrite are provided on the bonding film, thereby enhancing the adhesion between the bonding film and the Al₂O₃ layer and preventing the peeling of the coating layer. Patent Document 1 discloses that the dendrite is Ti (CO) or Ti (CNO) and that the branched protrusion is (TiAl) (CNO). Patent Document 1 describes that after the formation of the dendrite, the flow of a source gas is stopped once, and while the temperature is maintained, the pressure and the type of the source gas are changed to form the dendrite having a composition different from that of the dendrite.

RELATED ART DOCUMENTS Patent Document

Patent Document 1: Japanese Patent No. 5303732

SUMMARY

A coated tool of the present disclosure is provided with a base member and a coating layer located on a surface of the base member. The coating layer includes a TiCNO layer and an Al₂O₃ layer. The Al₂O₃ layer is located in contact with the TiCNO layer at a position farther from the base member than the TiCNO layer is. The TiCNO layer includes a composite protrusion including a first protrusion that projects toward the Al₂O₃ layer, a second protrusion that projects from the first protrusion in a direction intersecting a direction in which the first protrusion projects, and a third protrusion that projects from the second protrusion in a direction intersecting the direction in which the second protrusion projects. A cutting tool of the present disclosure is provided with: a holder extending from a first end toward a second end and including a pocket on a side of the first end; and the above-described coated tool located in the pocket.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view illustrating an example of a coated tool of the present disclosure.

FIG. 2 is a schematic view for explaining a configuration of a cross-section of a coating layer in the coated tool of FIG. 1 .

FIG. 3 is an enlarged view of a main part of the coated tool of the present disclosure for explaining a configuration in the vicinity of the TiCNO layer and the Al₂O₃ layer.

FIG. 4 is an enlarged view of the main part of the coated tool of the present disclosure for explaining the configuration in the vicinity of the TiCNO layer and the Al₂O₃ layer.

FIG. 5 is a schematic view for explaining a configuration of a cross-section of another form of the coating layer in the coated tool of the present disclosure.

FIG. 6 is a plan view illustrating an example of the cutting tool of the present disclosure.

EMBODIMENTS

<Coated Tool>

In the example illustrated in FIG. 1 , the coated tool of the present disclosure includes a main surface in a substantially rectangular plate-like shape. However, the main surface is not limited to this shape. A coated tool 1 includes a first surface 2 and a second surface 3 and includes a cutting edge 4 on at least a part of a portion where the first surface 2 and the second surface 3 intersect. The first surface 2 is a surface called a rake surface, and the second surface 3 is a surface called a flank surface. Hence it can also be said that the cutting edge 4 is provided on at least a part of a portion where the rake surface 2 and the flank surface 3 intersect.

As illustrated in a schematic view for explaining a configuration of a cross-section of a coating layer 7 in the coated tool 1 illustrated in FIG. 2 , the coated tool 1 includes a base member 5 and a coating layer 7 located on a surface of the base member 5.

A material constituting the base member 5 of the coated tool 1 may be a hard alloy, a ceramic or a metal. The hard alloy may be a cemented carbide including tungsten carbide (WC) and an iron-group metal such as cobalt (Co) or nickel (Ni). Another hard alloy may be a Ti-based cermet including titanium carbonitride (TiCN) and iron-group metals such as cobalt (Co) or nickel (Ni). The ceramic may be Si₃N₄, Al₂O₃, diamond or cubic boron nitride (cBN). The metal may be carbon steel, high-speed steel or alloy steel. If used as the coated tool 1, the base member 5 is favorably made of the cemented carbide or cermet among the materials described above in terms of fracture resistance and wear resistance.

The coating layer 7 includes a TiCNO layer 9 and an Al₂O₃ layer 11. The Al₂O₃ layer 11 is in contact with the TiCNO layer 9 at a position of the TiCNO layer 9 far from the base member 5.

As illustrated in FIG. 3 , the coated tool 1 of the present disclosure includes a first protrusion 13 a projecting toward the Al₂O₃ layer 11. A second protrusion 13 b is provided projecting from the first protrusion 13 a in a direction intersecting a direction in which the first protrusion 13 a projects. Further, a third protrusion 13 c is provided projecting from the second protrusion 13 b in a direction intersecting the direction in which the second protrusion 13 b projects. Hereinafter, a composite of the first protrusion 13 a, the second protrusion 13 b, and the third protrusion 13 c is also referred to as a composite protrusion 14.

In the coated tool 1 of the present disclosure, the first protrusion 13 a projects toward the Al₂O₃ layer 11, the second protrusion 13 b projects from the first protrusion 13 a in the direction intersecting the direction in which the first protrusion 13 a projects, and the third protrusion 13 c projects in the direction intersecting the direction in which the second protrusion 13 b projects. Hence the TiCNO layer 9 and the Al₂O₃ layer 11 are less likely to peel off due to the engagement of the first protrusion 13 a, the second protrusion 13 b, and the third protrusion 13 c with the Al₂O₃ layer 11. In FIG. 2 , the second protrusion 13 b and the third protrusion 13 c are omitted, otherwise the figure would be complicated.

The first protrusion 13 a, the second protrusion 13 b, and the third protrusion 13 c in the coated tool 1 of the present disclosure may all include Ti, C, N and O, and have homogeneous compositions. With the first protrusion 13 a, the second protrusion 13 b, and the third protrusion 13 c having the homogeneous compositions, the first protrusion 13 a, the second protrusion 13 b, and the third protrusion 13 c are less likely to be cracked or broken, and the adhesion between the TiCNO layer 9 and the Al₂O₃ layer 11 is improved as compared with a case where each protrusion has a different composition.

That the first protrusion 13 a, the second protrusion 13 b, and the third protrusion 13 c have the homogeneous compositions means that the difference among the respective constituents is 5% or less.

In addition, the deviation among each composition may be 3% or less. The deviation may be 1% or less.

The first protrusion 13 a, the second protrusion 13 b, and the third protrusion 13 c can be obtained by using the same gas during the formation of the first protrusion 13 a, the second protrusion 13 b, and the third protrusion 13 c.

The first protrusion 13 a and the second protrusion 13 b may have different compositions. The second protrusion 13 b and the third protrusion 13 c may have different compositions.

For the first protrusion 13 a, the second protrusion 13 b, and the third protrusion 13 c having different compositions, gases having different compositions are preferably used during the formation of the respective protrusions.

The coated tool 1 of the present disclosure may include a plurality of third protrusions 13 c on the second protrusion 13 b, as illustrated in FIG. 3 . With such a configuration, the adhesion strength between the TiCNO layer and the Al₂O₃ layer increases. That the second protrusion 13 b includes a plurality of third protrusions 13 c means that one second protrusion 13 b includes a plurality of third protrusions 13 c.

As illustrated in FIG. 3 , the third protrusion 13 c may protrude in a direction toward the first protrusion 13 a. With this configuration, the adhesion strength between the TiCNO layer 9 and the Al₂O₃ layer 11 increases.

In addition, the TiCNO layer 9 may include a plurality of second protrusions 13 b on the first protrusions 13 a, thereby making the TiCNO layer 9 and the Al₂O₃ layer 11 even less likely to peel off. That the first protrusion 13 a includes a plurality of second protrusions 13 b means that one first protrusion 13 a includes a plurality of second protrusions 13 b.

As illustrated in FIG. 3 , the second protrusion 13 b may project in a direction toward the base member 5. That the second protrusion 13 b projects in the direction toward the base member 5 means a state where an axis of the second protrusion 13 b intersects the base member 5 when being extended, the axis connecting the apex of the second protrusion 13 b and the midpoint of the width of a portion that is the origin of the projection of the second protrusion 13 b in the cross-section as illustrated in FIG. 3 .

In the cross-section as illustrated in FIG. 3 , the width of a portion of the first protrusion 13 a, the portion being the origin of the projection from the TiCNO layer 9, may be larger than the width of the portion of the second protrusion 13 b projecting from the first protrusion 13 a, the portion being the origin of the projection from the first protrusion 13 a. The length of the first protrusion 13 a may be larger than the length of the second protrusion 13 b projecting from the first protrusion 13 a. Note that the length of the first protrusion 13 a means a distance between the apex of the first protrusion 13 a and the midpoint of the width of the portion that is the origin of the projection of the first protrusion 13 a. Similarly, the length of the second protrusion 13 b means a distance between the apex of the second protrusion 13 b and the midpoint of the width of the portion that is the origin of the projection of the second protrusion 13 b. The average length of the first protrusions 13 a may be 10 to 500 nm.

In the cross-section orthogonal to the surface of the base member 5, the average width of the bases of the first protrusions 13 a may be 40 to 200 nm. The average length of the first protrusions 13 a may be 10 to 500 nm. Further, the average length of the first protrusions 13 a may be 50 to 300 nm.

The width of the base of the first protrusion 13 a is the width of the portion that is the origin of the projection of the first protrusion 13 a. The average value of the widths of the bases of the first protrusions 13 a is the average value of widths of bases of 20 or more first protrusions 13 a. The length of the first protrusion 13 a means the distance between the apex of the first protrusion 13 a and the midpoint of the width of the portion that is the origin of the projection of the first protrusion 13 a. The average length of the first protrusions 13 a is the average value of lengths of 20 or more first protrusions 13 a. Similarly, the length of the second protrusion 13 b means a distance between the apex of the second protrusion 13 b and the midpoint of the width of the portion that is the origin of the projection of the second protrusion 13 b.

The average width of the bases of the first protrusions 13 a may be 60 to 120 nm. The average length of the first protrusions 13 a may be 150 to 230 nm. If the first protrusion 13 a has such a shape, the difference between the longest first protrusion 13 a and the shortest first protrusion 13 a becomes small. If the first protrusion parts 13 a are relatively uniform as described above, the TiCNO layer 9 and the Al₂O₃ layer 11 are even less likely to peel off.

The average length of the first protrusions 13 a may be four times or less the average width of the bases of the first protrusions 13 a. With such a structure, the first protrusion 13 a is less likely to be broken, so that the TiCNO layer 9 and the Al₂O₃ layer 11 are even less likely to peel off. The average length of the first protrusions 13 a may be three times or less the average width of the bases of the first protrusions 13 a. As the ratio becomes smaller, the first protrusion 13 a is less likely to be broken, so that the TiCNO layer 9 and the Al₂O₃ layer 11 are even less likely to peel off. In particular, the average length of the first protrusions 13 a may be 2.5 times or less the average width of the bases of the first protrusions 13 a.

The length of the second protrusion 13 b may be 10 to 150 nm. The maximum width of the second protrusion 13 b may be 50 nm or less. The length of the third protrusion 13 c may be 10 to 70 nm. The maximum width of the third protrusion 13 c may be 20 nm or less.

The length of the third protrusion 13 c may be shorter than the length of the second protrusion 13 b. With such a structure, the first protrusion 13 a and the second protrusion 13 b are less likely to be broken, and the TiCNO layer 9 and the Al₂O₃ layer 11 are less likely to peel off. As a result, the fracture resistance of the coated tool 1 is improved.

The length of the third protrusion 13 c may be larger than the length of the second protrusion 13 b. With such a structure, even if the number of composite protrusions 14 is small, the TiCNO layer 9 and the Al₂O₃ layer 11 are less likely to peel off.

In comparison between the length of the third protrusion 13 c and the length of the second protrusion 13 b, the respective average lengths are compared.

The first protrusion 13 a may not be formed perpendicularly to the first surface 2 of the base member 5 but may be inclined relative to the first surface 2 of the base member 5.

If the thickness of the TiCNO layer 9 is in the range of 10 nm to 35 nm, the hardness of the TiCNO layer 9 does not decrease, and the Al₂O₃ layer 11 has an α-crystal structure. Here, the thickness of the TiCNO layer 9 excludes the first protrusion 13 a, the second protrusions 13 b, and the third protrusions 13 c.

The TiCNO layer 9 may include, for example, 30 to 70% by atom of titanium, 1 to 70% by atom of carbon, 1 to 35% by atom of nitrogen, and 3 to 20% by atom of oxygen. Further, the TiCNO layer 9 may include 10% by atom or less of aluminum. The TiCNO layer 9 may include 1 to 10% by atom of a component such as chlorine or chromium. The TiCNO layer 9 may include other minor components.

In the coated tool 1 of the present disclosure, the TiCNO layer and the first protrusion 13 a, the second protrusion 13 b, and the third protrusion 13 c may all have the same composition and may be within the composition range described above.

The TiCNO layer 9 including the first protrusions 13 a can be formed on the surface of the base member 5 by chemical vapor deposition (CVD) method under the following conditions.

The base member 5 may be placed in a chamber of a film formation apparatus, and the TiCNO layer 9 may be formed by, for example, making the following settings: a film formation temperature is 900° C. to 990° C., gas pressure is 5 kPa to 40 kPa, and a reactive gas composition is 3% by volume to 15% by volume of titanium tetrachloride (TiCl₄) gas, 3% by volume to 10% by volume of methane (CH₄) gas, 3% by volume to 50% by volume of nitrogen (N₂) gas, 0.5% by volume to 2.0% by volume of carbon monoxide (CO) gas, and the rest being hydrogen (H₂) gas. If the nitrogen (N₂) gas in the reactive gas composition is set to 30% by volume to 50% by volume, the average width of the bases of the first protrusions 13 a tends to be wide and the average length of the first protrusions 13 a tends to be short. In other words, under such a condition, it is easy to obtain the first protrusion 13 a that is thick, short, and less likely to be broken.

In a later stage of the formation of the TiCNO layer 9, if the film formation temperature is set to the range of 900 to 940° C. by lowering the film formation temperature without changing the composition of the source gas, the second protrusion 13 b is formed. The film formation time may be 30 to 90 minutes in total.

In the later stage of the formation of the TiCNO layer 9, that is, in the step of forming the second protrusions 13 b, if the film formation time is extended, the number of second protrusions 13 b increases, and the widths and lengths thereof tend to increase. The second protrusion 13 b, with its projecting direction extending toward the base member 5, is easily formed. Further, if the film-forming time is prolonged, the third protrusion 13 c projecting from the second protrusion 13 b is formed. That is, the composite protrusion 14 is formed.

After the formation of the TiCNO layer 9, the Al₂O₃ layer 11 can be formed by making the following settings: the film formation temperature is 900° C. to 990° C., the gas pressure is 5 kPa to 20 kPa, and the composition of the reactive gas is 5% by volume to 15% by volume of aluminum trichloride (AlCl₃) gas, 0.5% by volume to 2.5% by volume of hydrogen chloride (HCl) gas, 0.5% by volume to 5.0% by volume of carbon dioxide (CO₂) gas, 0% by volume to 1.0% by volume of hydrogen sulfide (H₂S) gas, and the rest being a hydrogen (H₂) gas. The Al₂O₃ layer 11 may be made of α-alumina.

An example in which the TiCNO layer 9 and the Al₂O₃ layer 11 are sequentially formed on the base member 5 has been described. As illustrated in FIG. 5 , the coating layer 7 may include a first TiCN layer 15 and a second TiCN layer 17 sequentially from the base member 5. The TiCNO layer 9 and the Al₂O₃ layer 11 may be sequentially provided on the second TiCN layer 17. In addition, a surface layer 19 including Ti and N may further be provided on the Al₂O₃ layer 11. In FIG. 5 , the second protrusion 13 b, the third protrusion 13 c, and the composite protrusion 14 are omitted.

The surface layer 19 may be made of other materials except for titanium nitride, such as titanium carbonitride, titanium oxycarbonitride, or chromium nitride. The surface layer 19 may be made of a colored material and have a function of easily discriminating whether or not the cutting edge 4 has been used. The surface layer 19 may be provided with a thickness of 0.1 μm to 3.0 μm. In addition, a base layer (not illustrated) made of TiN may further be provided between the base member 5 and the first TiCN layer 15.

If the base member 5 includes components such as Co, carbon (C), or tungsten (W), the base layer has a function of preventing the diffusion of these components into the layer present on the base layer. For example, if the first TiCN layer 15 is present on the base layer, the diffusion of the above components into the first TiCN layer 15 is prevented, and the lowering of the hardness of the first TiCN layer 15 is prevented. Alternatively, the carbon component in the base member 5 may be diffused into TiN of the base layer to form TiCN. The thickness of the base layer may be set to 0.1 μm to 1.0 μm.

If the coated tool 1 of the present disclosure includes a first TiCN layer 15, the thickness of the first TiCN layer 15 may be set to 2 μm to 15 μm. The thickness of the second TiCN layer 17 may be set to 10 nm to 900 nm.

The first TiCN layer 15 is made of a so-called moderate temperature (MT)-TiCN layer. If the thickness of the first TiCN layer 15 is 2 μm to 15 μm, which is formed by forming the MT-TiCN layer using a raw material that includes titanium tetrachloride (TiCl₄) gas, nitrogen (N₂) gas, acetonitrile (CH₃CN) gas, or the like at a relatively low film formation temperature of 780° C. to 880° C., the first TiCN layer 15 has high wear resistance and fracture resistance.

The first titanium carbonitride crystal included in the first TiCN layer 15 may be a columnar crystal elongated in the thickness direction of the coating layer 7.

The second TiCN layer 12 is made of a so-called high temperature (HT)-TiCN layer. The HT-TiCN layer may be formed using titanium tetrachloride (TiCl₄) gas, nitrogen (N₂) gas, methane (CH₄) gas, or the like as a source gas and not including acetonitrile (CH₃CN) gas at a film formation temperature in the range of 900° C. to 1050° C. The film may be formed at a higher temperature than the first TiCN layer 15. The thickness of the second TiCN layer 17 may be from 10 nm to 900 nm.

Here, an interface layer (not illustrated) may be disposed between the first TiCN layer 15 and the second TiCN layer 17, the interface layer including 30 to 70% by atom of titanium, 15 to 35% by atom of carbon, 15 to 35% by atom of nitrogen, and 2 to 10% by atom of oxygen. The thickness of the interface layer may be from 5 nm to 50 nm.

Instead of forming the interface layer, a method may be used in which after the formation of the first TiCN layer 15, the film formation chamber is temporarily cooled, a sample is removed into the atmosphere, and then the sample is placed again in the film formation chamber to heat the film formation chamber, thereby forming the second TiCN layer 17.

The carbon content ratio to the total content of carbon and nitrogen included in the second TiCN layer 17 may be smaller than the carbon content ratio of the first TiCN layer 15. This leads to improvement in the hardness of the first TiCN layer 15. As a result, the wear resistance and the fracture resistance of the coating layer 7 are improved. Here, the carbon content ratio is the ratio (C/(C+N)) of the content of carbon to the total content of carbon (C) and nitrogen (N) included.

If the carbon content ratio of the first TiCN layer 15 is set to 0.52 to 0.57 and the carbon content ratio of the second TiCN layer 17 is set to 0.42 to 0.51, the wear resistance and the fracture resistance of the coating layer 7 are further improved. If the carbon content in the first TiCN layer 15 is set to 15 to 29% by atom and the nitrogen content is set to 22 to 35% by atom, the wear resistance and the fracture resistance of the coating layer 7 are further enhanced. If the carbon content of the second TiCN layer 17 is set to 13 to 24% by atom and the nitrogen content is set to 23 to 35% by atom, the adhesion between the second TiCN layer 17 and the Al₂O₃ layer 11 is enhanced.

If the first TiCN layer 15 includes 45 to 60% by atom of titanium, 15 to 29% by atom of carbon, and 22 to 35% by atom of nitrogen, the wear resistance and the fracture resistance of the coating layer 7 are higher. The first TiCN layer 15 may include 0.5% or less by atom of oxygen. If the second TiCN layer 17 includes 48 to 60% by atom of titanium, 10 to 20% by atom of carbon, and 15 to 25% by atom of nitrogen, the second TiCN layer 17 is not broken, and the adhesion between the second TiCN layer 17 and the Al₂O₃ layer 11 is high. The second TiCN layer 17 may include 1 to 10% by atom of oxygen.

That is, oxygen may be present in the first TiCN layer 15 and the second TiCN layer 17, and the oxygen present in the second TiCN layer 17 may be more than the oxygen present in the first TiCN layer 15.

Note that the carbon content and the nitrogen content in each of the first TiCN layer 15 and the second TiCN layer 17 are measured using an energy dispersive X-ray spectrometer (EDS) accompanying a transmission electron microscope (TEM).

The structure and thickness of each layer and the shape of a crystal constituting each layer are measurable by observing an electron microscope photograph (scanning electron microscope (SEM) photograph or transmission electron microscope (TEM) photograph) in a cross-section of the tool 1.

Further, the coated tool 1 is designed to perform a cutting process by bringing the cutting edge, formed at an intersection between the rake surface and the flank surface, into contact with a workpiece and can produce the excellent effects described above. In addition to the cutting tool of the present disclosure, the coated tool 1 of the present disclosure can be applied to various uses such as wear-resistant parts like sliding parts and molds, excavation tools, tools like edge tools, and impact-resistant parts, and in these cases as well, the coated tool 1 has excellent mechanical reliability.

Next, an example of a method for manufacturing the tool of the present disclosure will be described.

Firstly, metal powder, carbon powder or the like is suitably added to inorganic powder of carbide, nitride, carbonitride, oxide or the like, which can form a hard alloy constituting the base member by sintering, and these are mixed together, to prepare a mixed powder. Then, the mixed powder is used to be molded into a predetermined tool shape by a known molding method such as press-molding, casting molding, extrusion molding and cold isostatic pressing. The molded body is sintered in a vacuum or a non-oxidizing atmosphere to produce the base member described above. The surface of the base member is then subjected to a polishing process, and a cutting part is subjected to a honing process if desired.

Subsequently, a coating layer is deposited on the surface by chemical vapor deposition (CVD) method.

Firstly, a base member is placed in the chamber, and a TiN layer as a base layer is formed. The layer is formed by making the following settings: the film formation temperature is 800° C. to 940° C., the gas pressure is 8 kPa to 50 kPa, and the composition of the reactive gas is 0.5% by volume to 10% by volume of titanium tetrachloride (TiCl₄) gas, 10% by volume to 60% by volume of nitrogen (N₂) gas, and the rest being hydrogen (H₂) gas.

Next, a first TiCN layer is formed. The layer is formed by making the following settings: the film formation temperature is 780° C. to 880° C., the gas pressure is 5 kPa to 25 kPa, and the composition of the reactive gas is 0.5% by volume to 10% by volume of titanium tetrachloride (TiCl₄) gas, 5% by volume to 60% by volume of nitrogen (N₂) gas, 0.1% by volume to 3.0% by volume of acetonitrile (CH₃CN) gas, and the rest being hydrogen (H₂) gas. At this time, a mean crystal width of columnar crystals of titanium carbonitride constituting the first TiCN layer can be made larger on the side of the surface than on the side of the base member by increasing the content ratio of the acetonitrile (CH₃CN) gas in a later stage of the film formation than in an initial stage of the film formation.

Then, an interface layer is formed on the first TiCN layer. The layer is formed by making the following settings: the film formation temperature is 900° C. to 1050° C., the gas pressure is 5 kPa to 40 kPa, and the composition of the reactive gas is 3% by volume to 30% by volume of titanium tetrachloride (TiCl₄) gas, 3% by volume to 15% by volume of methane (CH₄) gas, 5% by volume to 10% by volume of nitrogen (N₂) gas, 0.5% by volume to 10% by volume of carbon dioxide (CO₂) gas, and the rest being hydrogen (H₂) gas.

Next, a second TiCN layer is formed. The layer is formed by making the following settings: the film formation temperature is 900° C. to 990° C., the gas pressure is 5 kPa to 40 kPa, and the composition of the reactive gas is 1% by volume to 4% by volume of titanium tetrachloride (TiCl₄) gas, 5% by volume to 20% by volume of nitrogen (N₂) gas, 0.1% by volume to 10% by volume of methane (CH₄) gas, and the rest being hydrogen (H₂) gas.

Subsequently, a TiCNO layer 9 is formed. Firstly, the layer is formed by making the following settings: the film formation temperature is 940° C. to 990° C., the gas pressure is 5 kPa to 40 kPa, and the composition of the reactive gas is 3% by volume to 15% by volume of titanium tetrachloride (TiCl₄) gas, 3% by volume to 10% by volume of methane (CH₄) gas, 3% by volume to 25% by volume of nitrogen (N₂) gas, 0.5% by volume to 2.0% by volume of carbon oxide (CO) gas, and the rest being hydrogen (H₂) gas. Next, the film formation temperature is lowered to 900 to 940° C., and the layer is formed so that the total time is 30 to 90 minutes. Then, an Al₂O₃ layer is formed. The Al₂O₃ layer is formed by making the following settings: the film formation temperature is 950° C. to 1100° C., the gas pressure is 5 kPa to 20 kPa, and the composition of the reactive gas is 5% by volume to 15% by volume of aluminum trichloride (ACl₃) gas, 0.5% by volume to 2.5% by volume of hydrogen chloride (HCl) gas, 0.5% by volume to 5.0% by volume of carbon dioxide (CO₂) gas, 0% by volume to 1.0% by volume of hydrogen sulfide (H₂S) gas, and the rest being hydrogen (H₂) gas.

Then, a TiN layer which is a surface layer is formed. The layer is formed by making the following settings: the film formation temperature is 960° C. to 1100° C., the gas pressure is 10 kPa to 85 kPa, and the reactive gas composition is 0.1% by volume to 10% by volume of titanium tetrachloride (TiCl₄) gas, 10% by volume to 60% by volume of nitrogen (N₂) gas, and the rest being hydrogen (H₂) gas.

Thereafter, the polishing process is performed on at least a cutting part of the surface of the formed coating layer if desired. By the polishing process, the cutting part is smoothly processed to prevent the welding of the workpiece, and a tool with more excellent fracture resistance is obtained.

In the above example, the example has been shown where the first TiCN layer, the second TiCN layer, and the surface layer are provided, but the TiCNO layer and the Al₂O₃ layer may be directly laminated on the surface of the base member.

Although the coated tool 1 of the present disclosure has been described above, the present disclosure is not limited to the embodiment described above, and various improvements and modifications may be made within a range not departing from the gist of the present disclosure.

<Cutting Tool>

Next, the cutting tool of the present disclosure will be described with reference to the drawings.

As illustrated in FIG. 6 , a cutting tool 101 of the present disclosure is, for example, a rod-shaped body extending from a first end (upper end in FIG. 6 ) toward a second end (lower end in FIG. 6 ). As illustrated in FIG. 6 , the cutting tool 101 includes a holder 105 including a pocket 103 on a first end side (tip side), and the coated tool 1 located in the pocket 103. Because including the coated tool 1, the cutting tool 101 can perform a stable cutting process over a long period of time.

The pocket 103 is a part that permits attachment of the coated tool 1. The pocket 103 includes a seating surface parallel to a lower surface of the holder 105, and a constraining side surface inclined relative to the seating surface. The pocket 103 opens into a side of the first end of the holder 105.

The coated tool 1 is located in the pocket 103. At this time, the lower surface of the coated tool 1 may be in direct contact with the pocket 103, or a sheet (not illustrated) may be disposed between the coated tool 1 and the pocket 103.

The coated tool 1 is mounted on the holder 105 such that at least a part of a portion used as a cutting edge 4 at a ridge line where the first surface 3 and the second surface 5 intersect projects outward from the holder 105. In the present embodiment, the coated tool 1 is attached to the holder 105 with a fixing screw 107. That is, the coated tool 1 is attached to the holder 105 by inserting the fixing screw 107 into a through hole 17 of the coated tool 1, inserting the tip of the fixing screw 107 into a screw hole (not illustrated) formed in the pocket 103, and screwing the screw parts together.

As the material of the holder 105, steel, cast iron or the like can be used. Among these members, steel having high toughness may be used.

In the present embodiment, a cutting tool 101 used for a so-called turning process is exemplified. Examples of the turning process include an inner-diameter process, an outer-diameter process, and grooving process. Note that the cutting tool 101 is not limited to a tool used for the turning process. For example, the coated tools 1 of the above embodiment are applicable to the cutting tools for use in the milling process.

EXAMPLES

Firstly, an amount of 6% by mass of metal cobalt powder having a mean particle diameter of 1.2 μm, an amount of 0.5% by mass of titanium carbide powder having a mean particle diameter of 2.0 μm, an amount of 5% by mass of niobium carbide powder having a mean particle diameter of 2.0 μm, and the rest, namely, tungsten carbide powder having a mean particle diameter of 1.5 μm were added and mixed together. This was molded into a tool shape (CNMG120408) by press molding, followed by a debindering process. This was then sintered in vacuum at 1500° C. and 0.01 Pa for one hour, thereby manufacturing a base member composed of cemented carbide. The manufactured base member was then subjected to a brushing process, and a part of the base member which served as a cutting edge was subjected to round honing.

Next, the coating layer was formed on the above base member of cemented carbide by combining individual film formation conditions shown in Table 1 by chemical vapor deposition (CVD) method as described in Tables 2 and 3, thereby manufacturing a coated tool. In Table 1, each compound is represented by a chemical symbol.

The cross-section including the coating layer of the sample was subjected to SEM observation to observe the presence or absence of the first protrusion, the second protrusion, the third protrusion and the composite protrusion, and observes the forms of the first protrusion, the second protrusion, the third protrusion and the composite protrusion. Then, an intermittent cutting test was conducted using the obtained coated tool under the following conditions to evaluate the fracture resistance. Tables 2 and 3 show the test results.

<Intermittent Cutting Condition>

Workpiece: chromium molybdenum steel with four flutes (SCM440)

Tool Shape: CNMG120408

Cutting speed: 300 m/min

Feed speed: 0.3 mm/rev

Depth of Cut: 1.5 mm

Others: Using water-soluble cutting fluid

Evaluation item: The number of impacts before reaching peeling of Al₂O₃ layer was measured.

TABLE 1 Chamber temperature Pressure Time Condition Mixed gas composition (% by volume) (° C.) (kPa) (min) TiN TiCl₄: 1.0, N₂: 38, H₂: balance 850 16 180 TiCN-1 TiCl₄: 4.0, N₂: 23, CH₃CN: 0.4, H₂: balance 850 90 400 TiCN-2 TiCl₄: 4.0, N₂: 20, CH₄: 8.0, H₂: balance 950 13 80 TiCNO-01 TiCl₄: 4.0, N₂: 20, CH₄: 8.0, CO: 1.4, H₂: balance 970 10 60 TiCNO-02 TiCl₄: 4.0, N₂: 20, CH₄: 8.0, CO: 1.4, H₂: balance 970 10 30 TiCNO-03 TiCl₄: 4.0, N₂: 40, CH₄: 8.0, CO: 1.4, H₂: balance 970 10 30 TiCNO-1 TiCl₄: 4.0, N₂: 20, CH₄: 8.0, CO: 1.4, H₂: balance 940 10 10 TiCNO-2 TiCl₄: 4.0, N₂: 20, CH₄: 8.0, CO: 1.4, H₂: balance 940 10 30 TiCNO-3 TiCl₄: 4.0, N₂: 20, CH₄: 8.0, CO: 1.4, H₂: balance 940 10 60 TiCNO-4 TiCl₄: 4.0, N₂: 40, CH₄: 8.0, CO: 1.4, H₂: balance 940 10 10 TiCNO-5 TiCl₄: 4.0, N₂: 40, CH₄: 8.0, CO: 1.4, H₂: balance 940 10 30 TiCNO-6 TiCl₄: 4.0, N₂: 40, CH₄: 8.0, CO: 1.4, H₂: balance 940 10 60 Al₂O₃ AlCl₃: 3.7, HCl: 0.7, CO₂: 4.3, H₂S: 0.3, H₂: balance 950 7.5 380

TABLE 2 Coating layer TiCNO layer Average Average Cutting width length performance Film of first of first Al₂O₃ Number of Sample formation First Second Third protrusion protrusion layer impacts No. condition protrusion protrusion protrusion (nm) (nm) Condition (Ratio) 1 TiCNO-01 Present None None 30 150 Al₂O₃ 1 2 TiCNO-02 + TiCNO-1 Present Present None 20 95 Al₂O₃ 1.2 3 TiCNO-02 + TiCNO-2 Present Present None 30 140 Al₂O₃ 1.3 4 TiCNO-02 + TiCNO-3 Present Present Present 35 160 Al₂O₃ 1.5 5 TiCNO-03 + TiCNO-4 Present Present None 30 65 Al₂O₃ 1.3 6 TiCNO-03 + TiCNO-5 Present Present None 50 90 Al₂O₃ 1.4 7 TiCNO-03 + TiCNO-6 Present Present Present 70 135 Al₂O₃ 1.6

TABLE 3 Coating layer TiCNO layer Average Average Cutting width length performance Base First Second of first of first Al₂O₃ Number of Sample layer layer layer First Second Third protrusion protrusion layer impacts No. Condition Condition Condition Condition protrusion protrusion protrusion (nm) (nm) Condition (Ratio) 8 TiN TiCN-1 TiCN-2 TiCNO-01 Present None None 40 200 Al₂O₃ 1 9 TiN TiCN-1 TiCN 2 TiCNO-02 + Present Present None 30 130 Al₂O₃ 1.9 TiCNO-1 10 TiN TiCN-1 TiCN-2 TiCNO-02 + Present Present None 40 190 Al₂O₃ 2.2 TiCNO-2 11 TiN TiCN-1 TiCN-2 TiCNO-02 + Present Present Present 60 280 Al₂O₃ 2.5 TiCNO-3 12 TiN TiCN-1 TiCN-2 TiCNO-03 + Present Present None 60 120 Al₂O₃ 2.0 TiCNO-4 13 TiN TiCN-1 TiCN-2 TiCNO-03 + Present Present None 80 140 Al₂O₃ 2.3 TiCNO-5 14 TiN TiCN-1 TiCN-2 TiCNO-03 + Present Present Present 100 180 Al₂O₃ 2.6 TiCNO-6

In all of Samples No. 1 to 7 shown in Table 2, a TiCNO layer was formed directly on the base member, and an Al₂O₃ layer was formed thereon. In Sample No. 1 where the TiCNO layer was formed at 970° C. for 60 minutes, the first protrusion was formed, but the second protrusion and the third protrusion were not formed.

Table 2 describes how many times the number of impact times of Sample No. 1 each sample withstood, based on the number of impact times of Sample No. 1.

In samples No. 4 and 7 including the composite protrusions, an excellent cutting ability was obtained.

In all of Samples No. 8 to 14 shown in Table 3, a base layer, a first TiCN layer, and a second TiCN layer were formed on the base member, and a TiCNO layer and an Al₂O₃ layer are further formed thereon. In Sample No. 8 where the TiCNO layer was formed at 970° C. for 60 minutes, the first protrusion was formed, but the second protrusion and the third protrusion were not formed. In the sample where the film formation time was long, many second protrusions extending toward the base member were observed.

Table 3 describes how many times the number of impact times of Sample No. 8 each sample withstood, based on the number of impact times of Sample No. 8. In samples No. 11 and 14 including the composite protrusions, the excellent cutting performance was obtained.

As described above, the coated tool of the present disclosure has cutting performance superior to that of the sample without the composite protrusion.

When Sample No. 11 and Sample No. 14 were compared, the length of the first protrusion was smaller in Sample No. 14, but the length of the third protrusion was larger in Sample No. 14 than in Sample No. 11.

In sample No. 11, the average length of the second protrusions was larger than the average length of the third protrusions. On the other hand, in Sample No. 14, the average length of the third protrusions was larger than the average length of the second protrusions.

DESCRIPTION OF THE REFERENCE NUMERAL

1: Coated tool

2: Rake surface

3: Flank surface

4: Cutting edge

5: Base member

7: Coating layer

9: TiCNO layer

11: Al₂O₃ layer

13 a: First protrusion

13 b: Second protrusion

13 c: Third protrusion

14: Composite protrusion

15: First TiCN layer

17: Second TiCN layer

19: Surface layer

101: Cutting tool

103: Pocket

105: Holder

107: Fixing screw 

The invention claimed is:
 1. A coated tool, comprising: a base member; and a coating layer located on a surface of the base member, wherein the coating layer comprises a TiCNO layer and an Al₂O₃ layer, the Al₂O₃ layer is located in contact with the TiCNO layer at a position farther from the base member than the TiCNO layer is, and the TiCNO layer comprises a composite protrusion comprising a first protrusion, having a first protrusion base on the TiCNO layer and a first protrusion distal end that projects toward the Al₂O₃ layer, a second protrusion, having a second protrusion base on the first protrusion and a second protrusion distal end, and a third protrusion, having a third protrusion base on the second protrusion and a third protrusion distal end, wherein the third protrusion distal end is directed towards the first protrusion and/or the second protrusion distal end is directed towards the base member.
 2. The coated tool according to claim 1, wherein the composite protrusion comprises a plurality of the third protrusions on the second protrusion.
 3. The coated tool according to claim 1, wherein the third protrusion distal end is directed towards the first protrusion.
 4. The coated tool according to claim 1, wherein the composite protrusion comprises a plurality of the second protrusions on the first protrusion.
 5. The coated tool according to claim 1, wherein the second protrusion distal end is directed towards the base member.
 6. The coated tool according to claim 1, wherein an average width of bases of the first protrusions is 40 to 200 nm, and an average length of the first protrusions is 50 to 300 nm in a cross-section orthogonal to the surface of the base member.
 7. The coated tool according to claim 1, wherein an average length of the first protrusions is three times or less an average width of bases of the first protrusions.
 8. The coated tool according to claim 1, wherein an average length of the third protrusions in the composite protrusion is larger than an average length of the second protrusions.
 9. The coated tool according to claim 1, wherein the coating layer comprises a first TiCN layer, a second TiCN layer, the TiCNO layer and the Al₂O₃ layer sequentially from the base member.
 10. A cutting tool, comprising: a holder extending from a first end toward a second end and comprising a pocket on a side of the first end; and the coated tool according to claim 1, the coated tool being located in the pocket. 